2 files changed, 193 insertions, 0 deletions

diff --git a/fs/pipe.c b/fs/pipe.c
index e984beb93a0e..7fefb10db8d9 100644
--- a/fs/pipe.c
+++ b/fs/pipe.c
@@ -131,12 +131,19 @@ static int anon_pipe_buf_steal(struct pipe_inode_info *pipe,
         return 0;
 }
 
+static void anon_pipe_buf_get(struct pipe_inode_info *info,
+                              struct pipe_buffer *buf)
+{
+        page_cache_get(buf->page);
+}
+
 static struct pipe_buf_operations anon_pipe_buf_ops = {
         .can_merge = 1,
         .map = anon_pipe_buf_map,
         .unmap = anon_pipe_buf_unmap,
         .release = anon_pipe_buf_release,
         .steal = anon_pipe_buf_steal,
+        .get = anon_pipe_buf_get,
 };
 
 static ssize_t
diff --git a/fs/splice.c b/fs/splice.c
index 5d3eda64703b..8d57e89924a6 100644
--- a/fs/splice.c
+++ b/fs/splice.c
@@ -125,12 +125,19 @@ static void page_cache_pipe_buf_unmap(struct pipe_inode_info *info,
         kunmap(buf->page);
 }
 
+static void page_cache_pipe_buf_get(struct pipe_inode_info *info,
+                                    struct pipe_buffer *buf)
+{
+        page_cache_get(buf->page);
+}
+
 static struct pipe_buf_operations page_cache_pipe_buf_ops = {
         .can_merge = 0,
         .map = page_cache_pipe_buf_map,
         .unmap = page_cache_pipe_buf_unmap,
         .release = page_cache_pipe_buf_release,
         .steal = page_cache_pipe_buf_steal,
+        .get = page_cache_pipe_buf_get,
 };
 
 /*
@@ -963,3 +970,182 @@ asmlinkage long sys_splice(int fd_in, loff_t __user *off_in,
 
         return error;
 }
+
+/*
+ * Link contents of ipipe to opipe.
+ */
+static int link_pipe(struct pipe_inode_info *ipipe,
+                     struct pipe_inode_info *opipe,
+                     size_t len, unsigned int flags)
+{
+        struct pipe_buffer *ibuf, *obuf;
+        int ret = 0, do_wakeup = 0, i;
+
+        /*
+         * Potential ABBA deadlock, work around it by ordering lock
+         * grabbing by inode address. Otherwise two different processes
+         * could deadlock (one doing tee from A -> B, the other from B -> A).
+         */
+        if (ipipe->inode < opipe->inode) {
+                mutex_lock(&ipipe->inode->i_mutex);
+                mutex_lock(&opipe->inode->i_mutex);
+        } else {
+                mutex_lock(&opipe->inode->i_mutex);
+                mutex_lock(&ipipe->inode->i_mutex);
+        }
+
+        for (i = 0;; i++) {
+                if (!opipe->readers) {
+                        send_sig(SIGPIPE, current, 0);
+                        if (!ret)
+                                ret = -EPIPE;
+                        break;
+                }
+                if (ipipe->nrbufs - i) {
+                        ibuf = ipipe->bufs + ((ipipe->curbuf + i) & (PIPE_BUFFERS - 1));
+
+                        /*
+                         * If we have room, fill this buffer
+                         */
+                        if (opipe->nrbufs < PIPE_BUFFERS) {
+                                int nbuf = (opipe->curbuf + opipe->nrbufs) & (PIPE_BUFFERS - 1);
+
+                                /*
+                                 * Get a reference to this pipe buffer,
+                                 * so we can copy the contents over.
+                                 */
+                                ibuf->ops->get(ipipe, ibuf);
+
+                                obuf = opipe->bufs + nbuf;
+                                *obuf = *ibuf;
+
+                                if (obuf->len > len)
+                                        obuf->len = len;
+
+                                opipe->nrbufs++;
+                                do_wakeup = 1;
+                                ret += obuf->len;
+                                len -= obuf->len;
+
+                                if (!len)
+                                        break;
+                                if (opipe->nrbufs < PIPE_BUFFERS)
+                                        continue;
+                        }
+
+                        /*
+                         * We have input available, but no output room.
+                         * If we already copied data, return that.
+                         */
+                        if (flags & SPLICE_F_NONBLOCK) {
+                                if (!ret)
+                                        ret = -EAGAIN;
+                                break;
+                        }
+                        if (signal_pending(current)) {
+                                if (!ret)
+                                        ret = -ERESTARTSYS;
+                                break;
+                        }
+                        if (do_wakeup) {
+                                smp_mb();
+                                if (waitqueue_active(&opipe->wait))
+                                        wake_up_interruptible(&opipe->wait);
+                                kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
+                                do_wakeup = 0;
+                        }
+
+                        opipe->waiting_writers++;
+                        pipe_wait(opipe);
+                        opipe->waiting_writers--;
+                        continue;
+                }
+
+                /*
+                 * No input buffers, do the usual checks for available
+                 * writers and blocking and wait if necessary
+                 */
+                if (!ipipe->writers)
+                        break;
+                if (!ipipe->waiting_writers) {
+                        if (ret)
+                                break;
+                }
+                if (flags & SPLICE_F_NONBLOCK) {
+                        if (!ret)
+                                ret = -EAGAIN;
+                        break;
+                }
+                if (signal_pending(current)) {
+                        if (!ret)
+                                ret = -ERESTARTSYS;
+                        break;
+                }
+
+                if (waitqueue_active(&ipipe->wait))
+                        wake_up_interruptible_sync(&ipipe->wait);
+                kill_fasync(&ipipe->fasync_writers, SIGIO, POLL_OUT);
+
+                pipe_wait(ipipe);
+        }
+
+        mutex_unlock(&ipipe->inode->i_mutex);
+        mutex_unlock(&opipe->inode->i_mutex);
+
+        if (do_wakeup) {
+                smp_mb();
+                if (waitqueue_active(&opipe->wait))
+                        wake_up_interruptible(&opipe->wait);
+                kill_fasync(&opipe->fasync_readers, SIGIO, POLL_IN);
+        }
+
+        return ret;
+}
+
+/*
+ * This is a tee(1) implementation that works on pipes. It doesn't copy
+ * any data, it simply references the 'in' pages on the 'out' pipe.
+ * The 'flags' used are the SPLICE_F_* variants, currently the only
+ * applicable one is SPLICE_F_NONBLOCK.
+ */
+static long do_tee(struct file *in, struct file *out, size_t len,
+                   unsigned int flags)
+{
+        struct pipe_inode_info *ipipe = in->f_dentry->d_inode->i_pipe;
+        struct pipe_inode_info *opipe = out->f_dentry->d_inode->i_pipe;
+
+        /*
+         * Link ipipe to the two output pipes, consuming as we go along.
+         */
+        if (ipipe && opipe)
+                return link_pipe(ipipe, opipe, len, flags);
+
+        return -EINVAL;
+}
+
+asmlinkage long sys_tee(int fdin, int fdout, size_t len, unsigned int flags)
+{
+        struct file *in;
+        int error, fput_in;
+
+        if (unlikely(!len))
+                return 0;
+
+        error = -EBADF;
+        in = fget_light(fdin, &fput_in);
+        if (in) {
+                if (in->f_mode & FMODE_READ) {
+                        int fput_out;
+                        struct file *out = fget_light(fdout, &fput_out);
+
+                        if (out) {
+                                if (out->f_mode & FMODE_WRITE)
+                                        error = do_tee(in, out, len, flags);
+                                fput_light(out, fput_out);
+                        }
+                }
+                fput_light(in, fput_in);
+        }
+
+        return error;
+}